The Central Core Laboratory in the Department of Pathology consists of the Immunopathology, Cytogenetic and Molecular Pathology laboratories. The Immunopathology Laboratory (directed by Dr. F. Behm), has been dedicated to the processing immunophenotyping, cryopreserving and distribution of samples from patients with leukemia for over 12 years. Two full-time technologists supported by this grant perform the following activities: isolation of leukemic/mononuclear cells from patient samples for distribution to the institution's researchers; sample preparation for immunophenotyping and DNA Index determination; cell banking of cryopreserved leukemic and remission samples; and maintenance of the LEUCEL computer data base. The cytogenetics laboratory directed by Dr. S. Raimondi, karyotypes leukemic and remission samples by classic methodologies and by the technique of fluorescence in situ hybridization (FISH). Molecular Pathology, directed by Dr. J. Downing, performs molecular diagnostic and investigative studies of leukemic and remission samples using contemporary molecular biological techniques. The combined studies performed in these laboratories are required for (i) characterization of samples placed in the Cell Bank, (ii) detection of minimal residual disease in remission and bone marrow transplant patients as outlined in the section entitled Clinical Core D, (iii) direct support for projects 1, 2, 3, and 5.